Electric meter.



vPatented Apr. 29, |9Q2.

T. DUNCAN. ELECTRC METER. Y (Applicatun filled Aug. 21,*1899. Benewe-d Oct. 2, 1801.)

' 2 sheets-sheet 1.

To TRANSLATING DEVICES.

.. MV/ueyvtoz WW1/Lewes Nq. 698,65I. V Patented'Apr. 29,1902.

- T. DUNCAN.

' ELECTRIC METER. (Applicmmmed Aug, 21 ',v 1899. Renewed occ? 2, 1901.) (No Model.)

2 Shets-Sheet 2.

I WMM/Laboe@ UNITED STATES PATENT OFFICE.

THOMAS DUNCAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE SIEMENS & HALSKE ELECTRIC COMPANY OIF AMERICA, OF CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS.

ELECTRIC METER.

SIEGIFICATION forming, part of Letters Patent N o. 698,651, dated April 29, 1902. Application filed August 2l, 1899. Renewed October 2, 1901. Serial No. 77,300. (No model.)

To all whom, t may concern.-

Beit known that I, THOMAS DUNCAN, of

. Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Electric Meters, (Case No. 59,) of which the following is a specification.

This invention relates to improvements in alternating-current electric meters or measuring instruments -for use on circuits carrying heavy currents and in which series transformers are employed to reduce or transform the heavy current down to one of moderate or minute volume before subjecting the delicate mechanism of 'the meter toits influence. My previous application, filed May 24, 1899, Serial No. 718,023, (Case No. 5g) sets forth. a method of correcting the inaccuracy of the ordinary series transformer as employed in this connection by connecting the secondary circuit of the transformer in shunt around its primary and placinglthe series field-coil of understood from the following detailed description of the construction illustrated in the accompanring drawings, in which- Figure l is a somewhat diagrammatic View of a commutating wattmeter designed and connected in accordance with the present improvements. Fig. 2 is a still more diagrammatic view showing an adjustable resistance in the secondary circuit and means for varying the number of turns thereof. Fig. 3 shows a similar construction in indicatingwattmeters. Fig. a shows au induction inotor-meter constructed and connected in accordance with these improvements.

" In the drawings- Fig. 1,A and A" designate the main leads of the work-circuit, B the alternating-current generator, to the brushes ot" which the leads are connected. andC' the magnetic core of a series transformer the primary coil A2 of -which is connected in series in the main lead A.

l) designates thc series iicld-coils qfian ordinary commutating meter, and d d' theleads of a shunt-circuit leading around the primary a of lthe transformer and in which the coils D are connected.

E designates a'secondary coil wound on the transformer-core C and connected with thefore register as accurately as though its series coils were directly inserted inthe main line.

Obviously `this improvement may be employed with advantage in either ammeters or wattmeters. The instrument shown in Fig. l, however, is of the latter type and is provided with armature-coils F, which are connected through a commutator F in a shuntcircuit f f extending across the line between the main leads A A', a resistance f2 of suitable proportions being also provided in-this shunt-circuit. A disk F2 is secured upon the spindle F3 of the meter to rotate between drag-magnets G and retard the armature in a manner well understood. The rotations of the latter are then registered by anysuitable mechanism R, operatively connected with the spindle.

In the construction shown in Fig. 2 the same arrangement of the series field-coils D with relation to the secondary circuit E of the transformer obtains. Means of adjustment, however, are in this case provided in the 'form of a switch E', by means of which more or less of the turns of the coil E may be cutout, and in an adjustable resistance E2, which is also inserted in said secondary circuit.

Fig. 3 shows my improvements as embodied in an indicating-wattmeter, and Fig. -L in an indicating-wattmeter of the induction-motor type. In the former case the adjustable resistance El is depended on for adjust- Byv ment, While in the latter the switch 'or adjustable cut-out E is alone employed. The essential improvement in both cases is, however, the same as heretofore described, and it will beunderstood that Various other applications of the invention may be made Without involving any departure from the broad principle which underlies it.

I claim as my inventiont 1. The combination with a main circuit, of a transformer having its primary coil connected in series in said main circuit and lits secondary coil connected in shunt to its primary coil, and an energizing-coil also connected in shunt to the primary coil and in parallel with the secondary circuit.

2.. The' combination with a series transformer having its secondary connected in shunt to its primary circuit, of a measuring instrument or meter provided with an energizing-coil connected lin shunt to the primary circuit and in parallel with the secondary circuit.

3. The combination with the main circuit, of a transformer having its primary coil connected in series with the main circuit, and its secondary coil connected in shunt to its primary coil, an energizing-coil also connected in shunt to the primary coil and in parallel instrument or meter provided with an energizing-coil also` connected in shunt to the primary circuit and in parallel with the secondary circuit, and means for adj ustably Varying the number of turns in the secondary coil of ,the transformer.

5. The combination with a series transformer having its secondary connectedy in shunt to its primary circuit, of a measuring instrument or meter providedwith an energizing-coil also connected in shunt to the primary circuit of the transformer and in parallel with the secondary circuit, and means for adj ustably varying the resistance of said secondary circuit.

In testimony that I claim the foregoing as myinvention I afiix my signature, in presence of two subscribing witnesses, this 16th day of August, A. D. 1899.

- 'THOMAS DUNCAN. `Witnesses:

THOMAS W. PATTON, WILLIAM F. MEYER. 

